The far-right Alternative for Germany party has opened a convention after a strong performance in the recent European election, as opponents held large-scale protests and some demonstrators tried to block roads or clashed with police.

Alternative for Germany, or AfD, took 15.9% of the vote to finish second in the European Parliament election on June 9, despite a series of scandals and setbacks in recent months.

A particularly strong showing in the formerly communist east has bolstered its hopes of emerging as the strongest party in three state elections in that region in September.

At the regular two-day convention in the western city of Essen, co-leaders Alice Weidel and Tino Chrupalla are expected to seek another term in office.

A heavy police presence was in place in the city, where local authorities had tried to find a way to prevent the AfD event but lost their case in court.

Up to 100,000 people in total were expected at a string of counter-demonstrations and other events over the weekend, German news agency dpa reported.

On Friday evening, some 5,000 people participated in a peaceful anti-AfD rave titled Bass against Hatred, police said.

Early Saturday morning, a group of demonstrators tried to get through a barrier and were pushed back by police using pepper spray and batons.

There were also incidents in which masked demonstrators attacked officers, according to police, who reported “several” arrests.

Protesters staged sit-ins on streets and crossings near the convention hall.

Several AfD politicians said they had been picked up by police from their hotel and escorted to the venue, while other delegates were able to walk there without problems, dpa reported.

Ms Weidel told delegates as she opened the meeting that “what is going on out there has nothing to do with democracy” and vowed that “we are here and we will stay”.